Approximately thirty percent of all vaginal birth deliveries are complicated by some degree of cephalo-pelvic disproportion, or in other terms, the inability or difficulty of the maternal birth canal to accommodate the size of the fetal head. The fetal head, of course, typically represents the largest diameter of any section of a fetus and thus once the fetal head has protruded, completion of the delivery is simplified. In cases of extreme disproportion, the fetal head cannot engage and transabdominal delivery, i.e., Caesarean section, is necessary. However, in a number of cases the degree of disproportion is minimal and the fetal head will descend into the birth canal only to become trapped at the level of the maternal pubic ramus, unable to pass through due to the sharp angle which must be negotiated. In these cases, metal delivery forceps are employed to grasp the fetal head and either guide it or apply traction to it, to facilitate passage through the birth canal.
Such forceps are well known in medical literature as potentially dangerous to the well-being of the fetus and the mother. One of the primary disadvantages of forceps arises from the intense and locally concentrated pressures that known forceps apply to a fetal head. Such pressures are generally only applied to opposite sides of the fetal head and have resulted in permanent brain injury, bone and soft tissue injury (including enucleation, avulsion of the ear, facial nerve palsy, fracture of the mandible, fracture of the skull, etc.). In addition, the use of known forceps has also resulted in injury to the mother, including cervical and vaginal lacerations resulting in significant hemorrhage and requiring immediate attention by an obstetrician having considerable experience.
Although forceps for aiding in the delivery of a fetus have been in use for hundreds of years and hundreds of types of forceps have been produced since the introduction of the original Chamberlain forceps, all such forceps are based on the same mechanical principle, namely that of the tongs. More specifically, such known forceps comprise long and rigid shafts terminating in a blade-like member for controlling the fetal head and pivoted together such that application of force to the handles of such forceps results in the blade-like members moving towards or away from each other, but always in a single plane.
An additional deficiency of known forceps relates to an inherent difficulty or inability to apply purely tractive forces to a fetal head due to relative orientation of the fetal head, the forceps, the birth canal and the maternal pelvic bone structure. These problems and limitations have made it necessary to seek alternative methods to aid in fetal head delivery.
Illustrative of such alternate methods include the use of vacuum suction devices in which a cap-like device is placed on the fetal head, suction is applied and the fetus is withdrawn through the birth canal. For example, U.S. Pat. No. 3,765,408 to Kawai discloses a soft elastic vacuum cap having a plurality of recessed spaced apart orifices within an inner surface of the cap and close to an edge of the cap. Such orifices are commonly connected to a suction tube. In practice, the cup is inserted into the vagina and negotiated so as to contact the fetal head whereupon suction is applied and the fetus withdrawn.
U.S. Pat. No. 3,794,044 discloses delivery forceps comprising a plurality of retractable flexible fingers which are contoured generally to the shape of the fetal head. The device, with the fingers retracted into a hollow member, is inserted into the vagina until it abuts the fetal head, at which point the retracted fingers are extended and surround the fetal head. A noose portion attached to the finger tips is tightened and the fetus withdrawn. A thin membrane may be provided to interconnect the fingers and suction may be applied to further secure the fingers and membrane to the head.
Unfortunately, difficulty has been encountered in positioning such vacuum suction devices in the birth canal so as to adequately contact the fetal head. Furthermore, such devices tend to be large, cumbersome, bulky, complex and expensive. Additionally, although apparently and potentially an improvement over forceps, vacuum suction devices tend to suck the fetal head into the cap-like suction member, especially since the fetal head is relatively pliable, resulting in permanent scarring and other injury. More specifically, use of vacuum extraction on the fetus is believed to be a cause of trauma to the fetal scalp, fetal subgaleal hematosis, fetal scalp lacerations and skin necrosis. Fetal intracranial and intraocular hemorrhages have also been reported as a result of vacuum extraction, as has damage to the soft vaginal tissue of the mother. Extreme care must also be taken not to injure the fetus with any finger-like projections employed by the vacuum suction device.
U.S. Pat. No. 4,602,623 to Cherkassky discloses an apparatus comprising one or more sheets of material to be placed between the fetus and a wall of the birth canal. Such sheets have low coefficients of friction such that friction between the fetus and the canal wall is reduced during delivery.
U.S. Patent Nos. 13,453 to Buffum, 497,720 to Jones, 1,690,942 to Odell, 1,782,814 to Froehlich, 2,227,673 to Price and 2,792,838 to Guerriero generally disclose devices which may be placed around a fetal head often with the aid of finger-like members, tightened, and subsequently withdrawn.
Further known devices are disclosed in U.S. Pat. Nos. 4,018,230 to Ochiai et al. (an inflatable cervical dilator), 4,136,679 to Martinez et al. (a pistol-gripped spatula terminating in a solid scoop), 4,512,347 to Uddenberg (suction device comprising a rigid cap-like member), 3,592,198 to Evans (flexible cap-like member placed over fetal head and subsequently hardened through use of a thermosensitive compound to retain the fetal head).
U.S. Pat. Nos. 713,166 to St. Cyr and 4,597,391 to Janko disclose nets for delivery of a fetus, such nets having an end manually expandable for placement over a fetal head. However, the St. Cyr device requires two long rigid finger-like members for proper placement of the longitudinally slit net around a fetal head. The Janko device also requires a plurality of structural ribs to hold the general pattern of the longitudinally slit net. In each of these devices, the device as inserted is in the form of an elongated tube-like member and placed next to the fetal head. Only at this point may the device be opened and unfolded in a fan-like manner to surround the fetal head. During insertion of the device which is in the form of a tube-like member as well as during the subsequent unfolding process, the fetal head is continually prone to injury from the tip ends of the finger-like members. Additionally, once the net is unfolded, the finger-like projections must somehow mate and be joined to each other. Furthermore, the mechanical procedure of opening and unfolding the device, surrounding the fetal head and joining the end finger-like members exposes not only the fetus but also the mother to unnecessary and potentially harmful frictional forces. Extreme care must be taken so as to not injure the fetus with such finger-like members.
Due to the shortcomings of known devices described above, failure of medical personnel to accept such known devices and methods, and a decreased amount of training taught by medical institutions in the use of forceps and the resulting unfamiliarity with forceps of today's medical personnel, Caesarean section deliveries have become relatively common. Unfortunately, such Caesarean section deliveries are not without risks and complications, as is well documented in the medical field. Furthermore, there has been recent increased concern with the liberty with which Caesarean section deliveries are performed. Additionally, if a Caesarean section delivery is performed on a first birth, subsequent births are also likely to be by Caesarean section.